1. Field of the Invention
This invention relates to an apparatus and method for dissolving endothermic materials, without the use of fossil-fuel derived heat. This invention is especially suitable for dissolving agricultural chemicals such as urea, potassium chloride, ammonium nitrate, etc.
2. Description of the Art
Commercial plants for dissolving endothermic materials such as urea and potassium chloride generally require fossil fuel-derived heat for efficient operation. This is due to the negative heat of solution for endothermic materials such as solid urea. (The negative heat of solution for urea is approximately 109 BTUs per pound.) Thus, in the conventional fossil fuel-fired plant, hot water or steam and water at a temperature of approximately 180.degree. F., are mixed with urea to produce a solution having a temperature of about 90.degree. F. and 19 to 23 percent nitrogen. Unless adequate heat is supplied, this mixture becomes cold and rapidly approaches the crystallization temperature. Moreover the rate of dissolving is retarded and the production capacity is very low in the absence of sufficient heat.
It will be appreciated that it would be desirable to operate without fossil fuel-derived heat if such an operation could be economically carried out. Moreover, the elimination of fossil fuel from a process for dissolving endothermic material would be beneficial from the standpoint of conserving resources and, in addition, the pollution problems inherent in fossil fuel-derived heat would be avoided.
Thus it is one object of this invention to provide an energy efficient and economical method for dissolving endothermic materials without the use of fossil fuel-derived heat.
It is another object of the invention to provide a method and apparatus for dissolving endothermic materials which method and apparatus relies on natural environmental conditions, i.e. the weather.
It is another object of the invention to provide a process for dissolving endothermic materials which relies on the heat obtained from ambient air and thus it is particularly useful in locations wherein the average temperature of the ambient air is high, for example Hawaii.
Moreover, it is another object of this invention to take advantage of the temperature and humidity of the ambient air found in various locations to provide heat to a process for dissolving an endothermic material.
Finally, it is an object of the instant invention to provide a method and apparatus to prepare high concentrations of urea in water, for example 19 to 23 percent, by weight, nitrogen solutions, without the danger of crystallizing urea from such aqueous solutions and without the use of fossil fuel-derived heat.
Further objects and advantages are to provide improved steps, elements and arrangements thereof in a process effective in accomplishing the intended purposes.
Other objects and advantages of the instant invention will become apparent from a careful reading of the specification below.